If, during SMTP dialog, the STARTTLS command returns the following error:
454 4.7.1 TLS library initialization failure
and if you have certificates installed and working for pop/imap access, check the following:
Protections/ownerships of the certificates have to be set so mailsrv account can access the files
The directory where the certificates are stored need to have protections/ownerships set such that the mailsrv account can access the files within that directory.
After changing protections and installing certificates, you must run:
stop-msg dispatcher start-msg dispatcher
Restarting should work, but it is better to shut it down completely, install the certificates, and then start things back up.